1. Field of the Invention
The present invention relates to a digital broadcast receiver and an information updating method therefor.
2. Description of the Related Art
When a mobile body with a digital broadcast receiver moves from a receivable area of a physical channel (i.e., a channel occupying a particular frequency band defined as a unit) received by the digital broadcast receiver to an unreceivable area, viewing of a broadcast service provided by the physical channel becomes impossible. In such a case, a user manually operates the digital broadcast receiver to perform a channel scan to detect receivable physical channels, and selects a physical channel providing the same broadcast service from the detected physical channels.
Japanese Patent Application Publication No. 2011-61753 discloses a digital broadcast receiver having a function of automatically selecting a physical channel without manual operation as described above. While the digital broadcast receiver uses a first tuner/demodulator to perform channel selection for program viewing, it uses a second tuner/demodulator to perform a channel scan for sequentially selecting physical channels to detect receivable physical channels, and generates and stores receivable area information indicating a receivable area of each physical channel. When a reception state of a currently received physical channel is deteriorated, the digital broadcast receiver automatically switches from the currently received physical channel to another physical channel receivable at the current position based on the receivable area information and the current position.
Moreover, the above digital broadcast receiver represents a receivable area of a physical channel by a polygon. When a channel scan at the current position reveals that the physical channel can be received at the current position, if the current position is outside the existing receivable area, the digital broadcast receiver adds a new area having a vertex at the current position to the existing receivable area to extend the receivable area.
It is desired to efficiently extend a receivable area indicated by receivable area information in a digital broadcast receiver mounted on a mobile body.